Opportunities to photograph landscapes and water surfaces with smartphones have increased, so I tried this as a CPL filter that can suppress reflections. Since it is made by K&F CONCEPT, I ordered it with some expectations for the workmanship and texture. Unlike a typical spring type, the clip has a structure that moves up and down in parallel, so the sense of stability when attached to a smartphone is high. I was impressed that it was easy to set according to the lens position, and that it didn't shift easily even after wearing it. Since it is a 67mm diameter filter, it has a strong presence, but there is a sense of security that it can cover the entire lens well. The effect as a CPL is also easy to understand, and reflections on the water surface and glass are definitely reduced, and the color and contrast of the sky are naturally emphasized. The fact that you can fully enjoy the “feeling of using a filter” even when shooting with a smartphone was a good impression. It is also practical that it comes with a carrying bag and a rope to prevent loss as accessories. The lens surface can be protected when carrying, so you can use it safely even when shooting outdoors. One point that bothered me is that recent camera units feel that there is slightly less room for pinching when wearing a large smartphone or thick case. Also, with an ultra-wide-angle lens, vignetting may appear at the four corners, and in that case, it is necessary to zoom lightly to avoid it. Overall, I felt that it was an accessory that would take the expressive power of smartphone photography one step further. This product is highly recommended for those who want to use single-lens filters or those who want to enjoy filter work even with a smartphone.